Electronic signs are becoming popular in retail stores in order to keep pricing and sale information as current as possible. For example, prices can be kept up-to-date without having to reprint new price sheets whenever there is a sale or price change. The customer benefits by having the up-to-date information they need about the product pricing, and the retailer benefits by having programmable information that can be readily changed by various electronic means.
In the past, the challenge of electronic signs was addressed through the use of traditional display technologies, such as cathode ray tubes (CRTs), liquid crystal displays (LCDs), or plasma displays. These technologies provide dynamic, video-capable imagery, but in return require complex, expensive electronics and constant power. The advent of bistable display technologies has enabled a new breed of electronic sign, which utilizes an electronic “printhead” that is capable of updating display media as it moves past the head. This enables signage to be made with both reduced electronics and power consumption, and completely unique form factors.
One example of an electronic sign as discussed above is described in U.S. Pat. No. 6,269,225, to Sato et al., which discloses an electronically programmable display screen that is extendable. In U.S. Pat. No. 6,424,387, Sato et al. refine this idea to include a “feed-through” form of the design, wherein the display media can be ejected from one of two ports in the writehead. This format enables an optional display media design, in which the display has two symmetric writeable sections, one on each side of the media, so that the display can be viewed regardless of from which port it ejects.
Another example of an electronic sign is described in U.S. Pat. No. 6,498,597 to Sato et al., which discloses another system with an extendable, flexible display, but additionally proposes the use of a take-up spool to enable scrolling of long displays.
An alternative display system is set forth in U.S. Patent Application Publication No. US2003/0071800A1 to Vincent et al., wherein the display can be pulled out from and reinserted into the writehead to display one page of a book at a time.
One problem with the signage systems described above is the limitations in view direction of the displayed image. If reflective media is used, then the image is only viewable from one side. If transmissive media is used, the image can be viewed from either side, but it will be reversed, or mirror image, from one viewing direction. In either case, the display media is limited to a simple, two-dimensional display area, readable from only one viewing direction. Another problem with the above-described systems is that the writehead must have a sensing mechanism to recognize the end of the media to prevent overdriving that can damage the media or writehead.
There is a need for a bistable signage system, which has the reduced electronics and power requirements of existing bistable systems, yet is also capable of being viewed from multiple directions, and is not subject to failures due to overdriving.